Jessica is a boss in Crashlands. It is also Known as What Cannot Be Named. It breaths fire (fire damage), shooting explosions from her segments (poison damage), creates shooting plants (physical damage) , and charges at the player (physical damage). Jessica is usually called What Cannot be Named by the Brubus, especially Threshers.
Using a combination of the DBot and the Chrono Shifter can really help, if you have high DPS and Bicep Powers.
Always bring stocks of Anger Omelet and Bleghmar Treat, as they can increase damage output and critical chance of your pet respectively. Combine this with Vomma pet, one can defeat Jessica within minutes.
A Wompit or Bamli pet is also very useful, as each segment of Jessica's body takes damage separately, and the attacks can hit many segments, compounding the damage dealt. The flamethrower also deals area damage, making it very effective